Just to confuse the issue I am running 5w50 in my xB from Synlube - it's not really the oil weight but the oil friction reducers. Heavy oil clings to the cylinder walls and can build up in the piston rings more and throw the pistons out of balance with the oil buildup and slow them down if they get loaded up with heavy oil. Too light an oil and the rigns press through the oil film and you get metal to metal contact and rapid ring wear. Not enough oil pressure from too thin an oil and your rod bearings can hit the crank journals and spin causing scoring and damage - rod knock.

Enter again the classic problem with blanket fuel economy statements. As we've learned on GasSavers, that which helps a Neon doesn't always help a Honda. That which will work in a 3.0L engine won't work on a 1.5L engine.

I believe that some auto manufacturer's are less efficient in their design by default.

It shouldn't be much of a stretch to imagine someone getting an extra 20% out of a 25mpg Dodge and unable to do the same in a 40mpg Honda.

Anyway, I'm just rambling now.

Man that was an interesting article

https://www.lubedev.com/smartgas/additive.htm

AND LONG!! Phew I kept falling asleep - happens sometimes in the afternoons anyway - but very interesting that the results can vary with the engine. Maybe you guys with hondas that tried it should get some beauty supply acetone and some ethanol free gas and try it again. Going to have to try the 50-50 mix of Xylene and Acetone next fillup.

Oooops, Lol, I gave Badgett the link to that website in another thread.

I've tried everything on that site in my truck and a bunch of stuff on my car.
When it comes to the oil, just use the cheapest dino you can find. Then add the torco mpz and EAL to the oil. I got my best mpg doing that. That torco stuff has a ton of moly in it. I think the moly is mainly responsible for reducing friction and improving mpg.

Btw I have met the guy that owns that site, he's a decent honest guy, not trying to scam anyone. Some stuff may work for ya some might not, don't be afraid to experment;)

If the engine has low compression due to poorly sealing piston rings, heavier oil would raise the compression ratio, reduce blow-by and and result in better mileage. But in an engine in good condition, low viscosity oil should result in less friction and better mileage.

This was sarcasm :p

Oil -- Slippery Business
 

Ah Oil. Can't live with it, can't live without it.

Despite the recommendations for 5W-30 in all applications by the manufacturer in this case, I think a few considerations should be made.

• "Cold" Startup: is it -20 or 90F
• 5W-30 has the same viscosity whether synthetic or dino
• Just speculating, but wouldn't the manufacturer reccommend the most efficient oil to meet CAFE standards?
• Modern cars have many oil-pressure-based operations

First, I'd be more comfortable with a slightly heavier oil in extreme heat, and if operating under the "severe" maintenance schedule's conditions (maybe like a 10W-40).

Next, I have to throw-in that for viscosity's sake, 5W-30 Syn and Dino have the same "thickness", right?

Last, on a Honda with i-VTEC, you have a variety of critical engine components that run on oil pressure -- one of which is the variable valve lift actuator. If I had to guess, the cam timing adjuster probably runs on pressure as well. I wouldn't feel comfortable messing with the recommendation of Honda to run 5w-30 24/7/365.

For older, or less-complex engines (without VVT, etc.), perhaps 3 independent, monitored, double-blind experiments with a variety of oil weights and types will settle the arguement. I don't trust "testimonials" or manufacture-sponsored experiments unless independently monitored, and easily reproduced. Until then, as Matt said, a blanket statement for all cars and engines is useless, as we've learned.

RH77

Nice Article, Ben
 

I took a look at the crxMPG.com article: excellent breakdown of the claims, Ben. Also, the site is looking good! The DIY section is useful.

RH77

Aww, thanks rick. I need to update the site, or find a partner, but I'm so busy/lazy with life. Yar lar lar.

Yes, but only at the two specific SAE test temperatures. The advantage to fully synthetic oils is that their viscosity does not significantly increase as temperatures go lower than the cold test temp, nor does it significantly thin at higher than the hot test temperature. A 5w- synthetic will pump and flow more easily than a mineral based 5w- at temperatures lower than the standardized SAE test for winter rating of oil. It will also not thin out as much as a mineral based oil at temperatures above the SAE standard for hot viscosity rating. The full synthetic remains with a more consistent flow rate regardless of temperature.